Additive Manufacturing of Liquid‐Entrapped Architected Structures

Abstract This study presents a novel 3D printing process for combining two different phases of material: liquid and solid. A closed‐cell lattice structure designed for support‐free printing, allowing the entrapment of liquid in its empty spaces, thus forming a liquid‐entrapped architected structure. The structures are additively manufactured using a simultaneous printing and filling process without any post‐processing operation. This is achieved using a hybrid material extrusion (MEX) setup, which has a modified secondary nozzle that dispenses the liquid on demand after the primary nozzle finishes its layer printing process. This simultaneous printing and filling process requires no post‐processing operations and greatly reduces fabrication time. These structures are made using thermoplastic polyurethane (TPU) and subsequently filled partially (60%) and fully (100%) with silicone oil. Experimental and numerical quasi‐static compression tests are conducted on partially and fully filled global architected structures, and are compared with unfilled structures. A substantial enhancement in effective stiffness and energy absorption (EA) is observed in the post‐transition phase. By varying the quantity of liquid, effective stiffness and EA can be passively controlled with precision, to achieve tunable mechanical properties. The ability to tune the mechanical and functional properties holds great potential for a wide range of energy‐absorbing applications.